FROM SELECTION TO SUSTAINABILITY: BREEDING HEAT-TOLERANT CATTLE FOR A WARMING WORLD

Abstract

This review examines the current status of breeding strategies aimed at improving heat tolerance in cattle, a crucial response to the economic and physiological challenges posed by heat stress. Heat stress occurs when the temperature-humidity index (THI) exceeds an animal’s thermo-neutral zone, leading to reduced productivity and significant economic losses. While various mitigation strategies exist, genetic selection presents a sustainable, long-term solution. Advances in animal breeding now integrate traditional quantitative methods with molecular tools, enabling more precise selection for thermo-tolerance traits. Heritability estimates for rectal temperature under heat stress range from 0.13 to 0.17, indicating moderate potential for genetic improvement. Key genetic markers, such as heat shock proteins, are currently utilized in marker-assisted and genome-wide selection to identify and develop heat-tolerant bulls. For example, genomic breeding values for heat tolerance in Holstein and Jersey cattle have been developed with up to 30% reliability. Identifying the genetic mechanisms underlying thermal sensitivity and tolerance is essential for optimizing breeding programs. Combining molecular genetics with conventional approaches is recommended to enhance heat resilience in cattle, especially in regions facing rising temperatures due to climate change